In manufacturing starch by the wet-milling process, the grain is first soaked in warm water to soften the kernels. Soluble substances, such as sugars, proteins, and minerals, leach out of the kernel. This solution is drawn off the grain and part of the water is evaporated. The resulting concentrated solution is known as steepwater. If the evaporation is carried to completion, the residual solid material is known as steepwater solids.
Steepwater is generally added to fibrous milling residues to prepare animal feeds. Some steepwater is also sold as a fermentation nutrient. An early attempt to use steepwater as a lawn fertilizer did not give promising results. Although the grass started to grow more quickly after steepwater application, growth was not sustained, and the grass was easily injured if too much steepwater was applied.
It has now been discovered that when steepwater or steepwater solids are mixed with major plant nutrients (sources of nitrogen, phosphorus, and potassium) in proper proportions, an excellent plant food results. Such a product is more effective in increasing the growth of plants than either fertilizer containing the same amount of major plant nutrients or steepwater alone.
When ratios of nitrogen, phosphorus, and potassium are given herein, they refer to the conventional fertilizer ratios in which the nitrogen is given as "weight % N", phosphorus is given as "weight % P.sub.2 O.sub.5 ", and potassium is given as "weight % K.sub.2 O".